Process for producing photomechanical printing plates



No Drawing.

Patented Oct. 13, 1925.

UNITED STATES PATENT OFFICE.

AMBROS GALETZKA, OF DRESDEN, GERMANY, .ASSIGNOR OF ONE-HALF TOSKCHSISCHES SERUMWERK AKTIENGESELLSCHAFT, OF DRESDEN, GERMANY.

PROCESS FOR PRODUCING PHOTOMECHANICAL PRINTING PLATES.

T0 at whom/it may concern:

Be it known that I, AMBRos GALETZKA, a citizen of Saxonia, Germany,residing at Dresden, Germany, have invented certain new and usefulImprovements in Processes for Producing Photomechanical Printing Plates,of which the following is a specification. l

This invention relates to processes for producing photomechanicalprinting plates particularly plates for flat printingand letter pressprinting. An object of the invention is to produce printing plates whichmay be used for practically all printing processes, such as book,lithographic, photolithographic and offset printing and for all kinds ofprinting machines including special machines. A further object of theinvention is to produce printing plates which, in distinction from suchplates produced by other processes that require the use of particularkinds of paper (lithography: chalk paper, illustration printing withautotypes: enamelled paper, offset printing: well sized paper), enablesall kinds of paper and cardboard and also fabrics, metal sheet, wood,celluloid etc. to be directly printed upon.

The novel process enables types and pictures to be combined on one andthe same printing plate. The new process enables printing blocks forscreen pictures to be produced without necessitating the selection of aparticular width of screen on account of the roughness of the paper tobe printed p v -,A'fter these printing blocks havebeen produced, theymay be used directly in any kind of machine without any preparatoryoperations and give pictures which, as regards high lights and deepshades and the softness of half tones are equal to copper deep-printing.

The cost of producing the printing plates and the time required fortheir production is very small in comparison with other processes.

The novel printing plates can also be used for rotation printing and.enable the productionof sterotypes to be dispensed with.

The weight of the new printing plates is small so that the cost of thematerial 'of which they are made is correspondingly low. It thereforepays to keep them for impressions that might be subsequently required.

Application filed June 26, 1925. Serial No. 39,813.

The novel printingplates enable extreme 1y large editions to be producedwith uniform high class impressions. I

In the process which constitutes the present invention the base platemay consist of a plate of practically any kind of material, such aszinc, aluminum, glass, cellon, stone or the like on which if necessary athin coating' may be spread in a known manner to ensure the adhesion ofthe next layer. This thin coating may consist for example of a mixtureof gelatme water-glass and chromealum. I

A non-sensitive layer of elastic material is now placed on thethin'coating, this material being preferably such as will absorbmoisture and then swell up, and which in a moist state is elastic andrepels printing ink. For example a layer of pure gelatine may beemployed. The thickness of this layer may vary between wide limits.Thus, its thickness in a dry state may be 0.3 mms. and in a moist state0.5 mms. A sensitive layer which may consist of chromate gelatine oralbumin is spread on the elastic layer and the thickness of thesensitive layer may also vary. Its thickness may be 0.2 mms.

for example.

The different layers adhere firmly to each other, both when the gelatinelayer'is dry and when it is moistened, as when the upper layer isdeveloped after a photograph has been taken on it or during printing. Inorder to make the gelatine layer, when dry. incapable of absorbingmoisture and traces therewith of sensitive substances, such asbichromate, from the sensitive layer spread or poured upon it, thegelatine layer maybe hardened on its surface a slight degree before thesensitive layer is placed upon it. This may be accomplished by asolution of alum. This hardening must only be suffi- "cient to preventthe absorption of moisture during the short drying period of thesensitive layer. The hardening must not, however, be such as to preventthe absorption of moisturewhen the gelatine' layer is subjected for along time to the action of water, as for example during the developmentof the plate.

Thepicturethat is to be printed is now photographed on the plateprepared as described above. This may be done by exposing the platebeneath a negative, whereupon the finest pores so that they can easilybe washed out. 'After the water has been active for a considerable timeit commences penetrating from the sides into the gelatine surfaceslocated beneath the exposed surface elements so that finally the entiresurface of the gelatine layer is completely moistened and caused toswell up uniformly in its entirety. Theexposed parts of the surface ofthe upper layer are also lifted when the gelatine layer swells andremain in a common plane. The printing plate is now ready and afterprinting ink being rolled onto it it may be used for printing. printingplate can be regarded ,as a letter press printing form because theprinting surfaces project a distance equal to the thickness of theuppermost layer. The sensitive layer can, however, be made so thin thatthe printing plate can be regarded as a flat printing form. In bothcases the printing ink is repelled by the moist gelatine at the whitesurfaces 10- cated between the printing surfaces. The negative may bethe photogram of a line drawing or a type printing sheet. It may.however, also be a screen negative.

Print and illustrations or pictures may be copied'on the same printingplate, so that a mixed printing plate can be immediately produced. As itis only necessary to pro duce one photogram before printing, the typeemployed is immediately available for at er purposes. This has theadvantage that the printer only requires a small quantity of type andthis small quantity even is not subjected to wear. A further advantageis that, since it is possible to reduce and enlarge the objects ofphotographic means, the printer is not limited to a certain size oftypeand can carry on his work with onlyfafew sizes of types. Furthermore hecaniobt am any desired size of printed sheet by photographic reductionand enlargement.

All of the impression producing surface elements, even the smallestscreen spots have an elastic support. Consequently even a screen pictureproduced with a very narrowmeshed screen can be printed on rough paper.But as the thickness of the elastic intermediate layer is considerablysmaller than the thickness of the rubber plates in oflset printing, thedanger in the latter process that the various impression producingsurface elements will be squashed flat during printing so as to givefalse toning, is

avoided.

As the surface elements WhlCll are not to lent impressions, pictureswith rich contrasts produce an impression repel the printing ink bytheir moist gelatine, it is not neces sary to deepen these parts as inthe case of a Iine-electro or to allow the small screen spots to remaineven at the lightest parts as in the caseof an autotype block. In thenovel process, irrespective of the size of the surfaces, the lightestparts need not have any screen spots and require no deepening.

. In order to use the new printing plates for rotation printing it isonly necessary to bend them in the form of a cylinder and to fix them onthe cylinder of the machine.

The rapid and cheap production of the printing plates, the avoidance ofall etching and engraving, the absence of any transf'erring operation,the avoidance of all operations preparatory to printing the possibilityof employing the novel printing plates in any kind of printing machine,the fact 35 that special kinds of printing paper are not 3 necessary,the avoidance of a large quan-- tity of type and of a large number ofdifferent sizes of types, the obtaining of exceland soft middle tones byextremely simple means, and the possibility of printing large editionsensure an extensive use of the novel process in the most variousbranches of printing.

I claim 2-- 1. Process for producing printing plates consisting inplacing an elastic, nonsensitive layer on a base, placing a sensitivelayer on the non-sensitive layer, and transferring the object to beprinted onto the sensitive layer by photographic means. 7

2. Process for producing printing plates consisting in placing anelastic, non-sensitive, ink-repelling layer on a base, placing asensitive layer on the non-sensitive layer, and transferring the objectto be printed onto the sensitive layer by photographic means.

3. Process for producing printing plates consisting in placing anelastic, non-sensitive, inlcrepelling, moisture absorbing layer on abase, placing a sensitive layer on the non-sensitive layer, andtransfering the object to be rinted onto the sensitive layer byphotograp ic means.

4'." Process for producing printing plates consisting in placing on abase an elastic, non-sensitive layer of material that swells when-moistened, placing a sensitive layer on the non-sensitive layer, andtransferring the object to be printed onto the sensitive layer byphotographic means. q

5. Process for producing printing plates consisting in placing on a basean elastic non-sensitive layer of gelatine, placinga sensitive layer onthe non-sensitlve layer, and transferring the object to beprinted ontothe sensitive layer b photographic means.

6. Process for pro ucing printing plates consisting in placing on a basean elastic non-sensitive layer of gelatine, hardening the surface of thegelatine layer, placing a sensitive layeron the non-sensitive layer,

and transferring the Object to be printed 5 onto the sensitive layer byphotographic means.

7 Printing plate consisting of a base, an

elastic non-sensitive layer on the base, and a sensitive layer v0n thenon-sensitive layer onto Whiclrthe object to be printed has 10 beentransferred by photographic means. In testimony whereofI alfix mysignature.

AMBROS GALETZKA.

